ABSTRACT Children's National Hospital (CNH) CRS Despite the substantial progress in the HIV epidemic, adolescents, and young adults (AYA) aged 13-24 years living with HIV have worse health outcomes compared to any other age groups in the United States (US). Children's National Hospital (CNH), provides comprehensive HIV prevention and treatment services to the majority of AYA from the District of Columbia (DC) eligible metropolitan area (EMA) including three national HIV epidemic hotspots—Washington, DC, and two Maryland counties (Montgomery and Prince George's). Within DC, which continues to have the highest rates of new HIV infection in the United States, AYA have a high HIV prevalence of 0.3%, and high incidence of sexually transmitted infections, placing them at substantial risk for acquiring HIV. Through universal HIV counselling and opt-out screening, CNH reaches out to thousands of AYA in the DC EMA yearly with HIV prevention and testing services. Currently ~300 primarily minority Black AYA are in care at CNH for pre-exposure prophylaxis and antiretroviral treatment. CNH has a longstanding history of collaboration within local, regional, and national scientific networks, including prior participation in the Adolescent Trials Network (ATN). CNH has served as a successful recruitment site to multiple industry-sponsored investigational new drug clinical trials and received an uninterrupted line of DC Department of Health funding for HIV prevention and testing for more than 10 years. CNH has well-established partnerships with local and regional community-based organizations and a strong track-record of leadership in AYA HIV research within the broader local community of academic and community-based investigators, including its active role in DC Center for AIDS Research and DC Cohort Study. The overarching goal of the proposed ATN CNH consortium site is to contribute to the Westat-led ATN Operation and Collaboration Center (OCC) long-term scientific impact while expanding its role in delivering direct public health impacts on the local, regional, and national HIV epidemic among AYA. To achieve this goal, CNH will: (a) actively participate in the development and implementation of the Westat-led ATN OCC clinical trials identified by the ATN Executive and Scientific Leadership Committees; (b) deliver innovative solutions to optimize recruitment, enrollment, and retention of AYA at multiple sites in the DC EMA in ATN studies and ensure local laboratory capacity and pharmacy support; (c) propose novel concepts, approaches, and methodologies in implementation and clinical science, and development and optimization of biomedical prevention and treatment tools for AYA; and (d) meaningfully contribute to the Westat-led ATN OCC leadership model through sustained CNH site and AYA community engagement, expanding network collaborations through established regional collaborations among clinical, academic, community-based AYA focused partners, local DOHs, and s...